Iniciado por babaluba

¿No te parece raro que durante tantos millones de años, desde la aparición de la vida en la Tierra, las condiciones ambientales se hayan mantenido lo suficientemente estables como para que la vida no se extinguiera?

¿Sabes las condiciones que tiene que tener la Tierra para que se pueda dar vida en él? (ya sé que en Star Trek hablarán de vida basada en el silicio que no necesite unas condiciones como en la Tierra, pero eso es ciencia ficción, hamijo)


Conditions for life

The optimum place for life as we know it on Earth2 to exist elsewhere in space would be a planet with features just like those of Earth. These include having a star very like our own sun (an exceptionally stable star),3 being the right distance from its sun,4 as well as having an orbit5 and speed of rotation6 that would maintain a suitable temperature range, and hence fulfil the ‘Goldilocks criterion’ — not too hot, not too cold, just right. Another essential would be the presence of liquid water — in living cells, water provides a liquid medium, necessary for amino acids and other organic molecules to mingle and react.7

Also needed would be an atmosphere that was non-poisonous,8 and which would also absorb or deflect lethal doses of ultraviolet light, x-rays, and gamma rays, as well as a magnetic field strong enough to deflect the solar wind (a stream of high-energy charged particles).9 Complex life forms would need oxygen to be present in the right proportion. Earth is just right for life.10

Notas:

1 E.g. the finding, in Western Australia, of fossilised microbes, in rocks supposedly 3.5 billion years old. Creation 15(4):9, 1993; Schopf, J.W., Science 260(5108):640-646, 1993. Return to text.
2 I.e. DNA-based. This rules out theoretical fantasies such as ‘silicon-based life’ and ‘sulfur-based life’. Return to text.
3 See Sarfati, J., The sun: our special star Creation 22(1):27-30, 1999. Return to text.
4 Earth’s average distance from the sun is 150 million km (93 million miles). At this distance, the energy received by Earth from the sun is just the right amount to maintain a temperature range on Earth mostly between 0°C and 40°C — the narrow limits required to sustain life. Some microbial organisms can tolerate lower or higher temperatures, but they are the exceptions not the rule. Return to text.
5 Earth’s orbit around the sun is very nearly a perfect circle; if the orbit were an elongated ellipse with the sun at one focus, Earth’s temperatures would be extremely high during closest approach and extremely low at the outer end of the orbit. Return to text.
6 If Earth’s speed of rotation were much slower, there would be extreme differences between day and night temperatures. If it were much faster, increased centrifugal forces would cause atmospheric gases to escape into space. Return to text.
7 See Sarfati, J., The wonders of water Creation 20(1):44-47, 1997. Return to text.
8 Carbon dioxide in large enough quantities is lethal to living organisms. On Earth it amounts to 0.03 % of the atmosphere; on Mars it is 95%. Return to text.
9 Earth has the right atmospheric density and magnetic field to achieve these objectives. Return to text.
10 This section adapted from Gitt, W., Stars and their Purpose, CLV, Bielefeld, Germany, pp. 141 ff., 1996. Return to text.